Eurotunnel, the struggling Channel tunnel operator, today said it needed more time to restructure its estimated £6bn debt.

The Anglo-French firm repeated previous warnings that it may not survive beyond next year without a financial restructuring.

"Eurotunnel is undergoing a profound reorganisation which is generating a substantial improvement in operational performance," the chairman, Jacques Gounon, said.

"But beyond this positive new dynamism, we cannot guarantee the future of the group in 2007 unless there is a global financial restructuring."

Eurotunnel is asking creditors for a new waiver period that would allow talks to continue until July 12, with a review planned in mid-May.

It would enable all creditors to come together for the first time to reach a "consensual financial restructuring plan", the company said.

A committee of creditors has already rejected a Eurotunnel proposal to write off two-thirds of the debt without the offer of shares in return. Creditors could call in the company's debt and take it into their own hands if it is unable to reach agreement with them.

Eurotunnel faces a number of changes to its finances in the next couple of years that will worsen its predicament, including the repayment of capital on its loans from the beginning of next year.

The company said operational changes had resulted in revenues growth of 1% to £541m in 2005. It also achieved the first improvement in revenues from its shuttle services - which were up up 4% at £295m - since 2002.

The figures were issued on a provisional basis as uncertainty over Eurotunnel's debt forced it to delay its annual data.

Eurotunnel has struggled since being founded in 1986, hit by the soaring costs of digging the Channel tunnel and delays in starting train services.

It also vastly overestimated revenues from freight operators and Eurostar to service its debt payments. Competition from low budget airlines has further increased the pressure.